Salmonella enterica outbreak in a banqueting hall in Jerusalem: The unseen hand of the epidemiological Ttriangle?

Background: Foodborne Salmonella enterica outbreaks constitute both a threat to public health and an economic burden worldwide. Objectives: To characterize the pathogen(s) involved and possible source of infection of an outbreak of acute gastroenteritis in a banqueting hall in Jerusalem. Methods: We conducted interviews of guests and employees of the banqueting hall, and analyzed food items, samples from work surfaces and stool cultures. Results: Of 770 persons participating in three events on 3 consecutive days at a single banqueting hall, 124 were interviewed and 75 reported symptoms. Salmonella enterica, serovar Enteritidis, phage type C-8, was isolated from 10 stool cultures (eight guests, one symptomatic employee and one asymptomatic employee) and a sample of a mayonnaise-based egg salad. Pulsed-field gel electrophoresis of the isolates revealed an identical pattern in the outbreak isolates, different from SE C-8 controls. A culture-positive asymptomatic employee was linked to all three events. After a closure order, allowing for cleaning of the banqueting hall, revision of food preparation procedures and staff instruction on hygiene, the banqueting hall was reopened with no subsequent outbreaks. Conclusions: It is often difficult to pinpoint the source of infection in S. enterica outbreaks. Using molecular subtyping methods, a link was confirmed between patients, a food handler (presumably a carrier) and a food item - all showing an identical specific Salmonella enterica serovar Enteritidis. Testing asymptomatic as well as symptomatic food handlers in outbreak investigations is imperative. Pre- and post-hiring screening might be considered as preventive measures; hygiene and sanitation education are essential.